The human knee includes a lateral meniscus and a medial meniscus between the femur and the tibia. The menisci provide stability to the knee joint. Either of the menisci may tear or split when subjected to certain forces. This injury, which is commonly referred to as torn cartilage in the knee, is painful and may limit mobility.
Torn cartilage is often treated by surgically removing the torn region of the meniscus. The surgery may be carried out, for example, with mechanical devices such as knives, scissors or rotary trimmers. However, these devices are too large to be readily usable in the very small space within the knee and are generally too slow. Also, it is difficult to reach certain regions of the meniscus with some of these devices, and the cut may be jagged.
Electrosurgery can also be used to remove the torn region of the meniscus. Electrosurgery involves the use of high-frequency current to cut tissue and/or to coagulate a vessel. Electrosurgery has been used for a variety of surgical procedures. However, one problem with using electrosurgery, or any other surgical device, for removing a region of the meniscus is that the space adjacent the menisci for carrying out the surgery is very confined. In addition, electrosurgery presents a danger of charring regions of the knee adjacent the meniscus.
One prior art electrosurgical meniscal cutting device utilizes a fixed electrode, which terminates in a free end. The exposed length of the electrode can be manually varied by moving a cannula along the electrode. However, cannula movement cannot be remotely controlled, and so the exposed length of the electrode cannot be varied remotely during surgery as would be desirable to accommodate changes in the height dimension of the meniscus. Consequently, repeated cuts may be necessary if the exposed length of the electrode is too short. Moreover, the overall length of the electrode is not variable, and so a maximum dimension of the electrode is continuously present in the confined space within the knee even when only a small portion of that length is required for cutting the thinner portions of the meniscus. Also, the electrode is not shielded during insertion so there is a danger of inadvertent burning or charring.